The jgi_summarize_bam_contig_depths program of MetaBAT2 uses by default all available threads (max. the number of samples).
Fixed the number of threads used with OpenMP OMP_NUM_THREADS environment variable.

PR checklist

• This comment contains a description of changes (with reason)
• If you've fixed a bug or added code that should be tested, add tests!
• If necessary, also make a PR on the nf-core/mag branch on the nf-core/test-datasets repo
• Ensure the test suite passes (nextflow run . -profile test,docker).
• Make sure your code lints (nf-core lint .).
• Documentation in docs is updated
• CHANGELOG.md is updated
• README.md is updated

Learn more about contributing: https://github.com/nf-core/mag/tree/master/.github/CONTRIBUTING.md